Conventionally, a coil unit is utilized for a magnetic resonance imaging apparatus, as also described in Japanese Patent Laying-Open Nos. 2003-79597 and 2008-67807. In recent years, as there has been a growing concern about environment, electric vehicles and hybrid vehicles are attracting attention, and a method using a coil unit to charge power through electromagnetic induction, resonance and the like is attracting attention as a method for contactlessly charging an in-vehicle battery from external power supply.
For example, Japanese Patent Laying-Open No. 7-67270 describes a contactless power feeding apparatus that includes a primary coil buried in the ground and a secondary coil mounted in a vehicle and utilizes an induced current generated in the secondary coil to charge a battery mounted in the vehicle.
Japanese Patent Laying-Open No. 2010-73976 describes a wireless power transfer apparatus that includes a power receiving device mounted in an electric vehicle and a power feeding device, and the power feeding device includes a communication coil for transmitting power and the power receiving device includes a communication coil for receiving power. The communication coil for transmitting power includes a primary coil and a resonant coil, and the communication coil for receiving power includes a primary coil and a resonant coil. The communication coil for transmitting power and the communication coil for receiving power transfer power wirelessly in a resonant power transmission method.